Crystals with the sillenite structure, grown in an oxygen-free (argon)
atmosphere, are investigated by the ac photovoltage method. It is fou
nd that the photoconductivity in red light is sharply higher (by two o
rders of magnitude) than in crystals grown in the presence of oxygen.
Such crystals can be used in interferometric devices. (C) 1997 America
n Institute of Physics.